Robin Prior opens this monumental military history by stating that Britain was the only power on the Allied side in both world wars to fight the regimes of Kaiser Wilhelm II’s Germany, Nazi Germany, fascist Italy, and imperialist Japan ‘from beginning to end’. Some might quibble. Was not 1937 the beginning of the war against Japan? But few could doubt that Britain’s sustained war effort in both world wars was remarkable. Even though victory often seemed uncertain and the cost in casualties, human grief, economic dislocation, and financial ruin was immense, the nation continued to exhibit ‘stern resolve’, believing that ‘conquer we must’.

The literature on Britain in the two world wars is vast. Prior, himself, is one of the most acclaimed historians of the Allied campaigns in Gallipoli and on the Western Front in 1914–18. This new book’s claim to originality lies in its focus on civil–military relations: that is, the political and military interface that decided where and how Britain would fight, and what resources it could mobilise for these campaigns.

Prior asks: what, if anything, was learned from one war to the next? Did Britain fight a more efficient war in 1939–45 than in 1914–18 and, if so, was that experience accountable for it? Was Churchill, the legendary wartime prime minister from 1940–45, a beneficiary of World War I when he was unceremoniously removed from office in the aftermath of the bungled Gallipoli campaign?